fix: use 'linux' runner and install python if missing

.gitea/workflows/ci.yml

@@ -3,30 +3,36 @@ name: CI
 on:
   push:
     branches: [ main ]
-  pull_request:
-    branches: [ main ]
 
 jobs:
   test:
-    runs-on: ubuntu-latest
+    runs-on: linux
     steps:
-      - name: Checkout
+      - name: Debug
         run: |
+          echo "Runner: $OSTYPE"
+          id
           pwd
-          ls -la
-      - name: Test Python
+      - name: Install Python
         run: |
-          python3 --version
-          pip3 --version
+          if command -v python3 &> /dev/null; then
+            echo "Python3 found"
+            python3 --version
+          else
+            echo "Python3 not found, installing..."
+            apt-get update -qq
+            apt-get install -y -qq python3 python3-pip > /dev/null 2>&1
+            python3 --version
+          fi
       - name: Install deps
         run: |
-          pip3 install -e ".[dev]"
-      - name: Run lint
+          pip3 install -e ".[dev]" --quiet
+      - name: Lint
         run: |
           ruff check src/
-      - name: Run type check
+      - name: Type check
         run: |
           mypy src/
-      - name: Run tests
+      - name: Test
         run: |
           pytest tests/ -v